Asynchronous Timewarp

The good news regarding the high performance cost of the Oculus Rift is that you're not without help. Asynchronous Timewarp (ATW) is a rendering technique that helps fill delays in rendering with a calculated intermediary frame.

In essence, ATW warps an image based on the user's head movement, giving the appearance of multiple rendered frames but actually only modifying one while the rest are generated. All rendered images need to be warped at a baseline level so they don't appear skewed when viewed through the lenses, so adding an extra step to the warping process is relatively inexpensive for your hardware.

ATW can go a long way in making up for lost time in your VR experience, but it's important not to rely too heavily on it, because like every other rendering trick, it has its limits. For instance, with purely rotational ATW, the user can experience positional judder, which causes objects close to the user to appear blurry or doubled noticeable.

This screenshot of a submarine interior, provided by Oculus, demonstrates the perceived effect of positional judder:

ATW calculations are relatively simple because they only take rotation into account. Lateral movement is an entirely different problem; in 2016 Oculus announced work on a complementary feature called Asynchronous Spacewarp, which will perform predictions for head position as well. We'll see Asynchronous Timewarp at work in a later chapter, when we focus on performance and optimization of VR experiences.